CHEM 343 Lecture Notes - Nucleophilic Addition, Nucleophilic Conjugate Addition, Nucleophile
Document Summary
Stereochemistry of nucleophilic addition reactions: re and si faces. Prochiral carbonyl carbon a carbonyl carbon bonded to two different substituents. The two faces may be classified as re or si according to the sequence rule. If the substituents viewed from a particular face appear clockwise in order of decreasing priority, then that face is re; if counterclockwise, then si. The reaction pattern (direct addition vs conjugated addition) depends on the nature of the nucleophile. Nucleophiles that are strong bases (such as rmgx, h-) tend to form direct addition products. Nucleophiles that are relatively weak bases (such as cyanide ions, amines, thiols, and halide ions) usually form conjugate addition products. Direct addition occurs more rapidly than conjugate addition, therefore, the direct addition product is formed first. When nucleophile is a strong base, the direct addition is irreversible and the resulting product will be the final product of the reaction.
